1. Field of the Invention
The present invention relates generally to oil and gas well completion and production. In particular, the present invention relates to hydraulically controlled packer structures and associated methods utilized in well completion and production activities.
2. Description of the Prior Art
It is well known in the art to provide a well packer between the outer casing and the production tubing of an oil or gas well to isolate and seal off production fluids. It is also well known to set such packers hydraulically. Examples of hydraulically set packers can be found in U.S. Pat. Nos. 3,456,723, 3,603,388 and 4,263,968. In the hydraulic packers of the prior art, the setting of the packer would lock the packer in place within the outer casing of the well. To release the prior art packer required mechanical axial or rotational motion so that screws or other retaining means would shear and allow the packer to relax and be withdrawn from the well. In order to reuse the packer of the prior art, it was necessary to remove the packer completely from the well for reassembly with new shear screws or similar retaining means. Also, once set and locked, the packer could not be repositioned within the well bore. This made fine tuning of the packer's location relative to oil-bearing strata difficult.
The mechanical method for releasing prior art packers is particularly disadvantageous in wells containing multiple stacked packers. In these wells, the force required to shear the packers free requires the use of slip joints between packers set in close proximity to assure release of the packers individually. In addition, the modern trend toward intelligent completion components requires hydraulic and electrical conduits through packers. These conduits are easily damaged when mechanical releasing means are used.
Accordingly, there exists a need for a hydraulic packer that can be set, unset and reset prior to locking so that the packer location in relation to oil-bearing strata can be fine tuned and well completion components can be functionally checked. There is also a need for a hydraulic well packer that can be unset and reset without rendering the setting and locking mechanism inoperable so that the well packer can be easily relocated within the well casing without the need to retrieve and reassemble the well packer. Additionally, there is a need for a hydraulic well packer that can be released through application of hydraulic pressure rather than through mechanical axial or rotational motion to allow packer stacking and to protect hydraulic and electrical conduits. These needs are met by the present invention.